METHOD OF PREPARING RICE SHELL FOR PRODUCING HIGH-PURITY SILICON DIOXIDE Russian patent published in 2002 - IPC

FIELD: production of silicon dioxide. SUBSTANCE: method involves sizing, washing in cold and hot water, washing in acidic solution, collecting and removing floating rice shell particles, pressing under pressure of 0.01-10 MPa. Washing in hot water is performed in autoclave at temperature of at least 100 C and pressure of at least 0.101 MPa. Washing in acidic solution is performed at boiling temperature or in autoclave at temperature of at least 100 C and pressure of at least 0.101 MPa. Rice shell is additionally treated under vacuum, in aqueous solution of carbon dioxide and washed with aqueous alcoholic solution. After washing with acidic solution and water, vacuum treatment is provided by relieving pressure from atmospheric pressure value to 1-10 kPa for 0.01-1 s. Treatment with aqueous solution of carbon dioxide is performed in autoclave under pressure of at least 0.101 MPa for 1-6 hours. Rice shell is washed in aqueous 1-95% solution of ethyl or methyl alcohol in open bath or in autoclave at temperature of 50-150 C. EFFECT: simplified method and increased quality of silicon dioxide produced from rice shell. 4 cl, 1 tbl